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Shag Monitoring and Ringing

posted 24 Jun 2015, 05:52 by Ruth Dunn   [ updated 24 Jun 2015, 08:52 ]

Although the focus of my MRes project is the black-legged kittiwake, I have also been helping Nana with her shag nest monitoring. Puffin Island’s population of breeding European shag pairs is the largest colony in Wales and our monitoring focuses on approximately 80 nests across three areas: a beach in the south-west, a rocky ledge in the north and the main larger vegetated/ cliff section.

Basking Shags (main monitoring area)

European shags have been found to be good ecological indicators of the state of the marine environment because their behaviour and breeding success is heavily influenced by environmental factors and prey availability. It is therefore concerning that they are considered an amber listed species within Europe. Because they are coastal breeders which dive in order to forage for food, shags are also likely to be particularly sensitive to offshore marine developments and therefore monitoring their productivity is particularly important.

As Puffin Island is uninhabited by both humans and terrestrial herbivorous grazers, throughout summer the vegetation grows at an alarming rate. This has caused me some difficulty in locating some of the shag nests as the season has progressed – I often have to dive head first into guano-splattered bushes in order to observe the hidden contents of a nest. The adults guarding the nests also seem to be becoming less hospitable towards me. The hissing females are easier to ignore, but the rusty motorbike-like honking of the male shags can get a little exasperating by the end of the day!

Exhibiting excellent observation skills alongside Nana and a noisy male shag

Shags have variable breeding seasons which cover a number of months. This means that some of the Puffin Island nests still contain eggs (typically clutches of 3), whilst others are home to rather large chicks which are beginning to closely resemble their adult parents as opposed to scrawny, dinosaur-like lumps.

Neighbouring Shag Nests: A common clutch of three eggs; two young chicks

On Saturday I travelled to the island with the SCAN ringing group whose aim for the day was to ring shag and razorbill chicks (pulli). It was a busy day, made slightly trickier by the morning’s wet conditions turning the dried guano into a slippery layer that coated the rocks. Between 8.30am and 6.30pm the team managed to ring 135 shag pulli (as well as 164 razorbill pulli). Retrap highlights included a shag that was ringed as a chick in 2001, as well a razorbill adult from 1999 and chick from 2000.

Throughout the last few weeks many of the adults at the main nest site have also been colour ringed. This work, headed by Steve Dodd, will form part of a Retrapping Adults for Survival (RAS) monitoring project.

Combined with a handful of guillemot chicks, gull chicks and a few adults, the total number of birds ringed on Saturday was 423 – a successful day’s work!

A colour ringed adult